my pressure sensitivety is alll screwed up in gimp(I placed a link to the image in the comments, because i am a new user)

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http://askubuntu.com – i have unbuntu running on my laptop 11. whatever the current version is, and my tablet makes horizontal and vertical lines, when ever i draw something, example say im inking an picture or something a thunder bolt of paint shoots to the top and sides of my project, it basically looks like im tryna plot osmething on a map, i have went to edit and preferences and changed the setting to screen but this is whats causing the problem,, if i disable it then i loose pressure sensitivity, does any body have any ideas about what i should do, my other computer work fine just my laptop isn't working, my (HowTos)